Compact disc (CD) is a digitaloptical discdata storage format that was co-developed by Philips and Sony and released in 1982. The format was originally developed to store and play only sound recordings (CD-DA) but was later adapted for storage of data (CD-ROM). Several other formats were further derived from these, including write-once audio and data storage (CD-R), rewritable media (CD-RW), Video Compact Disc (VCD), Super Video Compact Disc (SVCD), Photo CD, PictureCD, Compact Disc-Interactive (CD-i), and Enhanced Music CD. The first commercially available audio CD player, the Sony CDP-101, was released October 1982 in Japan.

Standard CDs have a diameter of 120mm and can hold up to about 80 minutes of uncompressed audio or about 700 MiB of data. The Mini CD has various diameters ranging from 60mm80mm; they are sometimes used for CD singles, storing up to 24 minutes of audio, or delivering device drivers.

At the time of the technology's introduction in 1982, a CD could store much more data than a personal computerhard drive, which would typically hold 10 MB. By 2010, hard drives commonly offered as much storage space as a thousand CDs, while their prices had plummeted to commodity level. In 2004, worldwide sales of audio CDs, CD-ROMs and CD-Rs reached about 30 billion discs. By 2007, 200 billion CDs had been sold worldwide.

From the early 2000s, CDs were increasingly being replaced by other forms of digital storage and distribution, with the result that by 2010 the number of audio CDs being sold in the U.S. had dropped about 50 percent from their peak; however, they remained one of the primary distribution methods for the music industry. In 2014, revenues from digital music services matched those from physical format sales for the first time.[1]

History

American inventor James T. Russell has been credited with inventing the first system to record digital information on an optical transparentfoil that is lit from behind by a high-power halogen lamp.[2][3] Russell's patent application was filed in 1966, and he was granted a patent in 1970. Following litigation, Sony and Philips licensed Russell's patents (then held by a Canadian company, Optical Recording Corp.) in the 1980s.[4][5][6]

The compact disc is an evolution of LaserDisc technology, where a focused laser beamis used that enables the high information density required for high-quality digital audio signals.Prototypes were developed by Philips and Sony independently in the late 1970s.[7] Although originally dismissed by Philips Research management as a trivial pursuit, the CD became the primary focus for Philips as the LaserDisc format struggled.[8] In 1979, Sony and Philips set up a joint task force of engineers to design a new digital audio disc. After a year of experimentation and discussion, the Red BookCD-DA standard was published in 1980. After their commercial release in 1982, compact discs and their players were extremely popular. Despite costing up to $1,000, over 400,000 CD players were sold in the United States between 1983 and 1984.[9] By 1988, CD sales in the United States surpassed those of vinyl LPs, and by 1992 CD sales surpassed those of prerecorded music cassette tapes.[10][11] The success of the compact disc has been credited to the cooperation between Philips and Sony, which together agreed upon and developed compatible hardware. The unified design of the compact disc allowed consumers to purchase any disc or player from any company, and allowed the CD to dominate the at-home music market unchallenged.[12]

Digital audio laser-disc prototypes

In 1974, Lou Ottens, director of the audio division of Philips, started a small group with the aim to develop an analog optical audio disc with a diameter of and a sound quality superior to that of the vinyl record.[13] However, due to the unsatisfactory performance of the analog format, two Philips research engineers recommended a digital format in March 1974. In 1977, Philips then established a laboratory with the mission of creating a digital audio disc. The diameter of Philips's prototype compact disc was set at, the diagonal of an audio cassette.

Heitaro Nakajima, who developed an early digital audio recorder within Japan's national public broadcasting organization NHK in 1970, became general manager of Sony's audio department in 1971. His team developed a digital PCM adaptor audio tape recorder using a Betamax video recorder in 1973. After this, in 1974 the leap to storing digital audio on an optical disc was easily made.[14]Sony first publicly demonstrated an optical digital audio disc in September 1976. A year later, in September 1977, Sony showed the press a disc that could play 60 minutes of digital audio (44,100 Hz sampling rate and 16-bit resolution) using MFM modulation. In September 1978, the company demonstrated an optical digital audio disc with a 150-minute playing time, 44,056 Hz sampling rate, 16-bit linear resolution, and cross-interleavederror correction code—specifications similar to those later settled upon for the standard compact disc format in 1980. Technical details of Sony's digital audio disc were presented during the 62nd AES Convention, held on 13–16 March 1979, in Brussels. Sony's AES technical paper was published on 1 March 1979. A week later, on 8 March, Philips publicly demonstrated a prototype of an optical digital audio disc at a press conference called "Philips Introduce Compact Disc" in Eindhoven, Netherlands.

Collaboration and standardization

Sony executive Norio Ohga, later CEO and chairman of Sony, and Heitaro Nakajima were convinced of the format's commercial potential and pushed further development despite widespread skepticism.

As a result, in 1979, Sony and Philips set up a joint task force of engineers to design a new digital audio disc. Led by engineers Kees Schouhamer Immink and Toshitada Doi, the research pushed forward laser and optical disc technology. After a year of experimentation and discussion, the task force produced the Red BookCD-DA standard. First published in 1980, the standard was formally adopted by the IEC as an international standard in 1987, with various amendments becoming part of the standard in 1996.

Philips coined the term compact disc in line with another audio product, the Compact Cassette, and contributed the general manufacturingprocess, based on video LaserDisc technology. Philips also contributed eight-to-fourteen modulation (EFM), which offers a certain resilience to defects such as scratches and fingerprints, while Sony contributed the error-correction method, CIRC.

The Compact Disc Story, told by a former member of the task force, gives background information on the many technical decisions made, including the choice of the sampling frequency, playing time, and disc diameter. The task force consisted of around four to eight persons, though according to Philips, the compact disc was "invented collectively by a large group of people working as a team."

Initial launch and adoption

Philips established the Polydor Pressing Operations plant in Langenhagen near Hannover, Germany, and quickly passed a series of milestones.

The first commercial compact disc was produced on 17 August 1982, a 1979 recording of Chopin waltzes by Claudio Arrau.[15]

The first 50 titles were released in Japan on 1 October 1982, the very first of which was a re-release of the Billy Joel album 52nd Street.[16]

The first CD played on BBC Radio was in October 1982 on BBC Radio Scotland (Jimmy Mack programme, Followed by Ken Bruce and Eddie Mair all BBC Scotland), with the first CD played on UK independent radio station shortly after (Radio Forth, Jay Crawford Show). The CD was Dire Straits album Love Over Gold.[17]

The Japanese launch was followed in March 1983 by the introduction of CD players and discs to Europe[18] and North America (where CBS Records released sixteen titles).[19] This 1983 event is often seen as the "Big Bang" of the digital audio revolution. The new audio disc was enthusiastically received, especially in the early-adopting classical music and audiophile communities, and its handling quality received particular praise. As the price of players gradually came down, and with the introduction of the portable Discman the CD began to gain popularity in the larger popular and rock music markets. With the rise in CD sales, pre-recorded cassette tape sales began to decline in the late 1980s; CD sales overtook cassette sales in the early 1990s.[20][21]

The first artist to sell a million copies on CD was Dire Straits, with their 1985 album Brothers in Arms. One of the first CD markets was devoted to reissuing popular music whose commercial potential was already proven. The first major artist to have their entire catalog converted to CD was David Bowie, whose first fourteen studio albums of (then) sixteen were made available by RCA Records in February 1985, along with four greatest hits albums; his fifteenth and sixteenth albums had already been issued on CD by EMI Records in 1983 and 1984, respectively. On February 26, 1987, the first four UK albums by The Beatles were released in mono on compact disc. In 1988, 400 million CDs were manufactured by 50 pressing plants around the world.

Further development and decline

The CD was planned to be the successor of the vinyl record for playing music, rather than primarily as a data storage medium. From its origins as a musical format, CDs have grown to encompass other applications. In 1983, following the CD's introduction, Immink and Braat presented the first experiments with erasable compact discs during the 73rd AES Convention.[22] In June 1985, the computer-readable CD-ROM (read-only memory) and, in 1990, CD-Recordable were introduced, also developed by both Sony and Philips. Recordable CDs were a new alternative to tape for recording music and copying music albums without defects introduced in compression used in other digital recording methods. Other newer video formats such as DVD and Blu-ray use the same physical geometry as CD, and most DVD and Blu-ray players are backward compatible with audio CD.

U.S. CD sales peaked in 2000.[23] By the early 2000s, the CD player had largely replaced the audio cassette player as standard equipment in new automobiles, with 2010 being the final model year for any car in the United States to have a factory-equipped cassette player. With the increasing popularity of portable digital audio players, such as mobile phones, and solid state music storage, CD players are being phased out of automobiles in favor of minijack auxiliary inputs, wired connection to USB devices and wireless Bluetooth connection.

Meanwhile, with the advent and popularity of Internet-based distribution of files in lossily-compressedaudio formats such as MP3, sales of CDs began to decline in the 2000s. For example, between 2000 and 2008, despite overall growth in music sales and one anomalous year of increase, major-label CD sales declined overall by 20 percent, although independent and DIY music sales may be tracking better according to figures released 30 March 2009, and CDs still continue to sell greatly. As of 2012, CDs and DVDs made up only 34 percent of music sales in the United States.[24], only 24 percent of music in the United States was purchased on physical media, ⅔ of this consisting of CDs;[25] however, in the same year in Japan, over 80 percent of music was bought on CDs and other physical formats.[26] In 2018, U.S. CD sales were 52 million units — less than 6% of the peak sales volume in 2000.[23]

Despite the rapidly declining sales year-over-year, the pervasiveness of the technology remained for a time, with companies placing CDs in pharmacies, supermarkets, and filling station convenience stores targeting buyers least able to use Internet-based distribution. However, in 2018, Best Buy announced plans to decrease their focus on CD sales.[27][28][29]

Awards and accolades

Sony and Philips received praise for the development of the compact disc from professional organizations. These awards include

IEEE Milestone award, 2009, for Philips only with the citation: "On 8 March 1979, N.V. Philips' Gloeilampenfabrieken demonstrated for the international press a Compact Disc Audio Player. The demonstration showed that it is possible by using digital optical recording and playback to reproduce audio signals with superb stereo quality. This research at Philips established the technical standard for digital optical recording systems."

Physical details

A CD is made from 1.2mm thick, polycarbonate plastic and weighs 15–20 grams. From the center outward, components are: the center spindle hole (15 mm), the first-transition area (clamping ring), the clamping area (stacking ring), the second-transition area (mirror band), the program (data) area, and the rim. The inner program area occupies a radius from 25 to 58 mm.

A thin layer of aluminum or, more rarely, gold is applied to the surface, making it reflective. The metal is protected by a film of lacquer normally spin coated directly on the reflective layer. The label is printed on the lacquer layer, usually by screen printing or offset printing.

CD data is represented as tiny indentations known as pits, encoded in a spiral track moulded into the top of the polycarbonate layer. The areas between pits are known as lands. Each pit is approximately 100 nm deep by 500 nm wide, and varies from 850 nm to 3.5 µm in length.[30] The distance between the tracks (the pitch) is 1.6 µm.[31][32][33]

When playing an audio CD, a motor within the CD player spins the disc to a scanning velocity of 1.2–1.4 m/s (constant linear velocity) – equivalent to approximately 500 RPM at the inside of the disc, and approximately 200 RPM at the outside edge. The track on the CD begins at the inside and spirals outward so a disc played from beginning to end slows its rotation rate during playback.

The program area is 86.05 cm2 and the length of the recordable spiral is With a scanning speed of 1.2 m/s, the playing time is 74 minutes, or 650 MiB of data on a CD-ROM. A disc with data packed slightly more densely is tolerated by most players (though some old ones fail). Using a linear velocity of 1.2 m/s and a narrower track pitch of 1.5 µm increases the playing time to 80 minutes, and data capacity to 700 MiB.

A CD is read by focusing a 780 nm wavelength (near infrared) semiconductor laser through the bottom of the polycarbonate layer. The change in height between pits and lands results in a difference in the way the light is reflected. By measuring the reflection intensity change with a photodiode, data is read from the disc. In order to accommodate the spiral pattern of data, the laser is placed on a mobile mechanism within the disc tray of any CD player. This mechanism typically takes the form of a sled that slides across a rail driven by a worm gear, though some CD drives (particularly those manufactured by Philips during the 1980s and early 1990s) use a swing arm similar to that seen on a gramophone. This mechanism allows the laser to read information from the center to the edge of a disc without having to interrupt the spinning of the disc itself.

The pits and lands do not directly represent the 0's and 1's of binary data. Instead, non-return-to-zero, inverted encoding is used: a change from either pit to land or land to pit indicates a 1, while no change indicates a series of 0's. There must be at least two, and no more than ten 0's between each 1, which is defined by the length of the pit. This, in turn, is decoded by reversing the eight-to-fourteen modulation used in mastering the disc, and then reversing the cross-interleaved Reed–Solomon coding, finally revealing the raw data stored on the disc. These encoding techniques (defined in the Red Book) were originally designed for CD Digital Audio, but they later became a standard for almost all CD formats (such as CD-ROM).

Integrity

CDs are susceptible to damage during handling and from environmental exposure. Pits are much closer to the label side of a disc, enabling defects and contaminants on the clear side to be out of focus during playback. Consequently, CDs are more likely to suffer damage on the label side of the disc. Scratches on the clear side can be repaired by refilling them with similar refractive plastic or by careful polishing. The edges of CDs are sometimes incompletely sealed, allowing gases and liquids to enter the CD and corrode the metal reflective layer and/or interfere with the focus of the laser on the pits, a condition known as disc rot.[34] The fungus Geotrichum candidum has been found—under conditions of high heat and humidity—to consume the polycarbonate plastic and aluminium found in CDs.[35][36]

Sisaro, Ben. New York Times 11 June 2015: Web site: Music Streaming Service Aims at Japan, Where CD Is Still King. https://web.archive.org/web/20171020191923/https://www.nytimes.com/2015/06/12/business/media/line-music-a-new-streaming-service-aims-at-japanese-market.html?_r=0. 20 October 2017. live. 2017-08-26. dmy-all.